What are scabs in history?
Also asked, why are they called scabs?
The term "scab" was first used in the 13th century to mean a nasty, itchy skin disease or the crust that forms on a wound. By 1806, the word "scab" arrived at its current meaning -- a strikebreaker who willingly crosses the picket line [source: Lexicon of Labor, Online Etymology Dictionary].
Just so, who were the scabs?
A strikebreaker (sometimes derogatorily called a scab, blackleg, or knobstick) is a person who works despite an ongoing strike. Strikebreakers are usually individuals who were not employed by the company prior to the trade union dispute, but rather hired after or during the strike to keep the organization running.
By the late 1700s, laborers adopted the insult to refer to workmen who wouldn't join a strike, a union, or take part in organized labor. Just as a scab is a physical lesion, the strikebreaking scab disfigures the social body of labor—both the solidarity of workers and the dignity of work.